Electrical condenser



Aug. 9; 1932. w. DUBILIER ELECTRICAL CONDENSER Original Filed May 24,1921 INVENTOR Mam/v DUB/LIE? ATTORNEY Patented Aug. 9, 1932 p PATENTOFFICE UNITED STATES WILLIAM pUBILnm, or NEW YORK, 21. Y.,-

sssronon 'ro pnmmnn oonnnnsna conrona'rron, or mew YORK, 1v. Y.,.Aconroaa'rron or DELAWARE ELECTRICAL CONDENSER Original application filedMay 24, 1921, Serial m. 412,105. Patent 110. 1,575,044, dated March 2,1928. Divided and this application filed September 6, 1924. Serial No.736,311.

The invention has for an object to provide an electrical condenserinvolving the use of but. a relatively smallquantity of dielectric andconducting material,-and of simple structure, which nevertheless will becapable of withstanding use in high potential and high frequencycircuits without the production of undue resistance losses, brushdischarge, heating or other undesirable effects tending to injure ordestroy the same.

Further objects and advantages of the invention will be in part obviousand in part specifically pointed out in the description hereinaftercontained, which, taken in connection with the accompanying drawing,discloses a preferred embodiment thereof; such embodiment, however, isto be considered merely as illustrative of its principle. In thedrawing:

Figure 1 is a plan view of a condenser made in accordance with theinvention held in a suitable clamp, and in position in its casing.

Figure 2 is a side view of the structure shown in Figure 1, a portion ofthe clamp being cut away for clearness.

Figure 3 is a fragmentary sectional view showing a form of tap or leadwhich maybe used in connection with the condenser.

Figure 4" is a section on line 44 of Figure 2.

The same numerals identify the same parts throughout. i

This application is a division of my earlier patent No. 1,575,044,issuedMarch 2, 1926.

When condensers are designed for use in high potential or high frequencycircuits, it is desirable to bring about a subdivision of the potentialbetween diiferent parts of the condenser, in such manner that the strainat any given part will be reduced sufiiciently to enable the condenserto stand long continued use without undue deterioration due to brushdischarge, heating, or other causes. Furthermore, the conductingarmatures' or plates of condenser should bev capable of carrying thecurrent --for which it is designed, without theproduction of sufiicientheat to injure the condenser; in other words, the conducting platesshould be ofrelatively low resistance.

If a condenser of the above character be made up of constructingcondenser sections having a plurality of conducting plates of oppositepolarity interleaved with dielectric sheets, and connecting in series aplurality of such sections, it is necessary to employ several conductingsheets in each section to give the section sufiicient thickness andstrength to be handled without too great risk of injury; also thecurrent travels through the connected sections in the plane of theconducting plates, ,or through the sheets from end to end, thusfollowing a path of high resistance, so that, for this further reason asubstantial number of sheets in parallel are usually needed in eachsection toreduce the internal resistance of the condenser to a value lowenough to prevent heating to an undesirable degree.

From the above and other considerations it may result, particularlywhere condensers of low capacity are desired, that individual sectionsof the character above described necessarily will have such largecapacity,

that an unduly large number of such sections will have to be connectedin series to reduce the capacitv of the complete condenser to thedesired value and yet retain suflicient conductivity in the plates. Thusthe condenser becomes of large size, and involves increased expense onaccount of the amount of dielectric and conducting material used, andthe added labor of preparing and properlv assembling the same.

According to the present inventiom the conducting plates of thecondenser are so arranged that the current flows transversely throughthe same, instead. of from end to end. thus greatly reducing the lengthof the leaved with larger dielectric sheets 2 which I prefer to make ofsheet mica, and built up into a stack. Circuit is made to the plates 1which are at opposite ends of a series, and the intermediate plates arecompletely insulated, so that the dielectric sheets 2 may be permittedto overlap such plates on all four sides. Thus the intermediate platesact as floating capacities between the end plates, and the total.potential will be divided between all the plates, each pair of adjacentplates actin as a unit condenser. The current path 1s in a directiontransverse to the plane of the plates, and the cross-section of 'theconductive path equals the length of the plate multiplied by its width,instead of the width of the plate multiplied by its thickness; theincreased conductivity may be compared to what would be obtained bypassing current across an extended conductor, instead of along itslength. Also the length of the path of current travel is a function ofthe thickness of the plates, instead of their lcngth. With the condenserconstructed in the above manner, the internal resistance therefore isexceedingly low, and it is not necessary to use a large amount ofconducting material with the added dielectric sheets which would berequired, to carry the cur rent. Thus only that number of plates inseries need be used which is considered necessary to reduce the volta' eper unit condenser to a value which is considered safe, and eachadditional sub-division of voltage involves only one additionalconducting plate, and one die ectric sheet.

The required capacity and the potential of the circuit in which thecondenser is to be used being known the number of unit condensersnecessary to be connected in series may be selected, and a size ofconducting plate adopted which will give approximately the desiredcapacity when the selected number of unit condensers are placed inseries.

- Then by adding or removing one or more conducting lates, if necessary,the final capacity may be rought within the required limits, withoutunbalancing the distribution of potential over the unit condensers.

The number of unit condensers emplo ed 'in series for any givencondenser, shoul 'be such as to reduce the potential per unit condenserto a value below the brush discharge point. I prefer to employ as thedielectric,

'unitary mica sheetsaveraging about threethousandths of an inch inthickness, in which case the potential per unit condenser should notrise above a value in the neighborhood of 1000 or 1500 volts maximum,and in certain cases, particularly where the condenser is to-besubjected to undamped oscillations, I preferto reduce the potential tova value around 600 or 800 voltsmaximum.

Furthermore, in order to eliminate air,

v'acua moisture,,etc., and to renderithe di-- electric as homogeneous aspossible, I prefer to impregnate the condenser thoroughly with a heatedinsulating composition such as melted arafiim'or other suitablecompound, and subject the same to the action of a vacuum, after whichthe stack should be placed under a high compression of several tons, topress out substantially all the insulating compound from between theconducting plates and dielectric sheets, and bring about an intimatesurface contact between the same.

In some instances condenser stacks of the character above described maybe made up in one or more groups of standard sizes containing convenientnumbers of condenser units in series, and several such stock condenserstacks combined in series or parallel to make up a desired condenser.For example, where high potential condensers of very small capacity aredesired such as may be used with radio sets of the vacuum tube type,several standard groups may be placed end to end, thus formingacomposite block containing a proper number of unit condensers in seriesand having the desired low capacity. The form of condenser illustratedconsists of a plurality of series groups 3, 4, .5 and 6 which may be ofthe same or different individual capacities, as desired, and any desirednumber may be-employed to build up a complete stack. As' shown, aplurality of taps 7 are interposed between the several groups 3 to,6 andthus, by making the circuit connections to different taps, difi'erentcapacities may be obtained. The taps 7 conveniently may be made in theform of copper strips overlapped by the dielectric sheets 2 on threesides, but projecting beyond the latter on the fourth side, and plates 8of tin foil, similar to the plates previously described, may be placedon opposite sides of taps 7 to facilitate the making of an intimatecontact between the conducting material associated with taps 7 andadjacent dielectric sheets 2. Thus the taps need not render the stackloose or otheryvis; defective at the points from which they ea Thecondenser should be securely clamped to insure that the sheets'will beheld throughout in intimate surface contact as mentioned above, afterthe condenser has been put into actual use. 7

According to the present invention I place the stack within a casing 9,preferably of metal, with the sheets making up the stack disposedsubstantially parallel -to the end walls of thecasing, the taps 7projecting upwardly toward the open side of the casing. Thus one or moreterminal connections for the condenser may be led through the cover 10of the casing inany suitable way as in dicated in Fig. 2 to connect withthe taps. The condenser is surrounded by clamp 11 which fits within theside walls of casing 9, and thus the condenser may be assembled intoproper position within the clamp and.

the latter inserted into or withdrawn from the casing without disturbingthe stack. The clamp consists of the bearing members 12 and 13 atopposite ends of the stack, and the tension members lextend between thebearing members to transmit the strain from one end of the stack to theother; I prefer to make up the clamp from one continuous piece of metalsuch as spring steel, which may be dropforged, punched or pressed intoproper shape. The bearing block15 may then be interposed between onebearing member 13 and the adj acent end of the stack, and thecompression applied to the stack at a point substantially in line withthe centre by means of a binding member such as the stud 16 threadedthrough bearing member 13 and pressing on block 15. Thus the block 15will exert substantially uniform pressure upon the stack throughout theentire area and will not tend to bow or warp. The opposite bearingmember 12 may be made heavy enough to insure thatits surface whichpresses against the stack will be substantially flat. With proportionssimilar to those shown in the drawing, the bearing member 12 will berelatively rigid,- and any changes in shape in the clamp which may occurdue to the springiness of the material, when stud 16 is tightened up,will take place in its thinner portions, particularly where tensionmembers 14 join on to the bearing member 13, without affecting thecondenser stack detrimentally." Where the stack is combined with a clampof the above character, the clampor the casing or both may form oneterminal of the con denser, or'the clamp may be completely insulated, ifdesired. It will be noted that the clamp acts to-bridge electrically thespace between the groups 3 and Q, and thus if the taps 7 at oppositeends of group 4are connected to o posite circuit terminals, groups 3, 5and 6 W111 be in parallel with group 4 between the terminals. Thisarrangement may be adopted to give a relatively large capacity, or, ifdesired the sections 3, 5 and 6 may include suchlarge numbers of unitcondensers in series that the capacityof groups 3, 5 and 6 in series isnegligible as compared to the capacity of group 4, so that the resultantcapacity is substantiall that of group 4 alone. Similarly the num er ofunit condensers in series in group-4 may be so large as compared togroups 3, 5 and 6 that the capacity of group 4 may be disregarded, thenumber of unit condensers in the different groups 3 to 6 as illustratednot being in any way essential.

In mounting the condenser stack and its clamp within the casing 9, I-prefer to place the clamp parallel to the bottom of the easing in suchmanner that taps 7 will project upwardly toward the cover 10.Particuarly where the condenser is to be subjected to undampedoscillations, I prefer to construct the cover 10 of micasheetsimpregnated with an insulating compound such as parafiin', andpressed together as closely as possible to form a homogeneous sheetwhich may be suitably held in position over the casing 9 as by means ofa metal ring 17 and screws 18 which clamp the cover 10 between such ringand a shoulder 19 running around the upper edge of the casing. I

In order to facilitate the positioning of the clamp and condenser stackwithin the casing, the clamp may be attached to the cover before thelatter is afiixed to the casing; this is accomplishedin the presentinstance by a pair of straps 20 of thin metal or the like secured to theunder side of the cover by means of screws 21, and to the clamp byfurther screws 22; Thus the condenser clamp and stack may be positionedproperly with respect to the cover, and when the latter is secured tothe casing -9 the condenser stack will be'properly located in the casingwithout further adjustment. Ordinarily the casing will be filled withinsulating compound such as paraflimand the straps 20 thus serve to holdthe condenser in suspension in the insulating compound until the lattersolidifies.

vIn cases where thecasing or clamp are incudedin circuit withthe'condenser'stack, the straps 20 also may act as circuitconnectionsthereto,

' The clamp or member 11 may be regarded as a complete casing andthe-condenser sections or stacks 3, 4, 5 and 6 in it may be enclosedsimply by providing this clamp or casing 11 with top and bottom covers;and the clamp or casing 11 further may be employed with or without theexterior casing 9, which is simply a container. In any event theterminals or taps 7 extendthrough this casing 11 and are insulatedtherefrom, because they must project above the top of the clamp orcasingl l to be led out thru cover 10. Or the condenser sectionsconsisting of the conducting plates 1 with intervening dielectric sheets2 may be regarded as disposed in a vessel or casing 'which includes notonly the casing 9 but also the inside member 11, which is really a partof the casing, or supporting container for the condenser'sections, asthe clamping member is joined to the receiving container 9 and might bein circuit therewith if necessary through the metal straps 20, thescrews 18 and the screws 21.

L While a specific embodiment of the invention has been described, itwill'be obvious that many changes may ,be made therein withoutdepartingfrom the spirit of the invention as defined in the following claims.

I make no claim herein of the manner in 1 which the conducting plates 1and the dielectect by Letters Patent of the United States earlier patentabove-mentioned; and the claims herein being directed more partlcularlyto the'general combination of the body of the condenser mounted in theclamp 11,

and the arrangementof the terminals 7.

Having described my invention, what I believe to be new and desireto'secure and pro- 1. An electrical condenser comprising a plurality ofstacks of sheets, a common metal casing for said plurality of stacks bywhich casing said stacksare connected in series;

and a corresponding number of condenser terminals extending from thestacks through the casing and insulated therefrom. i

.2. In an electrical condenser, a plurality of stacks, a metal clampingmember surrounding said stacks and electrically onnecting'them in seriesand terminals electrically connected to said stacks.

3. In an electrical condenser, a plurality of stacks,,each comprising anumber of sections connected in series, a metal clamping membersurrounding said stacks and electrieally connecting them in series atadjacent ends thereof and terminals electrically connected to theopposite ends of the stacks.

4. In-an electrical condenser, a plurality of stacks, a metal clampingmember therefor electrically connecting certain of said stacks in seriesand terminals electrically connected to said stacks.

5. In an electrical condenser, a plurality of condenser stacks forming acondenser block, means for compressing said block of stacks comprisingan electrical connection whereby certain of said stacks are connected inseries, and terminals electrically connecting the series connectedstacksrin parallel with at least one other of said stacks.

6. In an electrical condenser, a plurality vof condenser stacks forminga condenser block, a'm'etal clamp for said block of stacks comprisingmeans for electrically connecting certain of said stacks in series, andterminals electrically connected to the stacks, the said clamp beingelectrically intermediate the said terminals.

7. An electrical condenser comprising a composite block of condenserstacks arranged end to end, means for applying pressure on the ends ofsaid block including means for connecting the end stacks in series, andterminals disposed between the said end stacks and another of the stacksand electrically connected thereto.

Signed at New York in the county of New York and State of New York this27th day of August A. D. 1924.

WILLIAM DUBILIER.

